This invention relates in general to vehicle transmissions and in particular to an assembly for sensing the movement of a transmission shift rail in and out of a central neutral position and for operating a neutral start switch in response thereto.
In most vehicles, a transmission is provided in the drive train between the engine and the driven wheels. As is well known, the transmission includes a case containing an input shaft, an output shaft, and a plurality of meshing gears. Means are provided for connecting selected ones of the meshing gears between the input shaft and the output shaft to provide a desired speed reduction gear ratio therebetween. The meshing gears contained within the transmission case are of varying size so as to provide a plurality of such gear ratios. Thus, by appropriate selection of these gear ratios, acceleration and deceleration of the vehicle can be accomplished in a smooth and efficient manner.
In a conventional vehicle transmission, a pivotable shift lever is provided for selecting and engaging a desired one of the gear ratios for use. The upper end of the shift lever extends upwardly into the driver compartment of the vehicle, where it can be grasped and manually moved by the driver. The lower end of the shift lever extends downwardly within the transmission case into cooperation with a plurality of shift rails. The shift rails are typically oriented in adjacent parallel fashion within the transmission case. Each of the shift rails is supported for longitudinal movement in opposite axial directions from a central neutral position to either of two gear engaging positions. Appropriate movement of the shift lever causes selection and longitudinal movement of one of the shift rails and, therefore, engagement of a desired gear ratio for use.
In vehicle transmissions of this general type, it is well known to provide a neutral start switch assembly for preventing the vehicle engine from being started unless all of the shift rails are in their central neutral positions. This is done to avoid unexpected vehicle movement caused by starting the engine while the transmission is in gear. Such neutral start switch assemblies typically include a normally closed switch, commonly referred to as a neutral start switch, which is connected in the ignition circuit of the vehicle engine. An actuator mechanism is provided for sensing when any one of the shift rails is moved out of its central neutral position and for opening the neutral start switch in response thereto. When this occurs, the ignition system of the vehicle engine is disabled and cannot be started.
A number of neutral start switch assemblies are known in the art for performing this function. However, these known assemblies have been found to be unduly complex in structure and space consuming within the transmission. Inasmuch as modern vehicle transmissions are becoming increasingly smaller in physical size, the space available within the transmission case for these neutral start switch assemblies is becoming increasingly limited. Thus, it would be desirable to provide an improved structure for a neutral start switch assembly which is simple in construction and compact in size.